1. Field of the Invention
This invention relates to improvements over an eye-refractometer device using retinoscopy.
2. Description of the Prior Art
Generally, in the measurement of diopter of an eye, it is necessary to first detect the direction of the astigmatic principal meridians, and then measure the diopter in that direction. A device for carrying out such measurement by the use of retinoscopy is already known. Retinoscopy is such that a slit-like light is sent into the pupil of the eye to be examined and when that light is moved, the movement exhibited in the pupil by the reflected light from the retina of the eye is observed, whereby the neutralized condition in which the light becomes unmoved is found out. There are two types of such method, namely, one in which a lens having various refractive powers is disposed immediately before the eye to be examined so that the eye is observed from a predetermined position to obtain the diopter by a lens bringing about the neutralized condition, and one in which the eye is observed by varying the observation distance so that the diopter is obtained from a distance providing the neutralized condition. As the devices for photoelectrically measuring the diopter of the eye by retinoscopy, a device using the former method is disclosed in U.S. Pat. No. 3,136,839 and a device using the latter method is disclosed in U.S. Pat. No. 3,715,166. In these measuring devices, the entire device is rotated to detect the direction of the astigmatic axis of the eye to be examined and an accurate servo mechanism for making the entire device exactly coincident with the direction of the astigmatic principal meridians is indispensable. This has made the device complicated and bulky and has been prejudicial to quick measurement.